Polyamide, particularly nylon 6, has been used extensively as a synthetic fiber. Its structural and mechanical properties make it attractive for use in such capacities as face fiber for carpeting.
Polyamide fibers, yarns, carpets, and fabrics are often heatset using either moist or dry heat to provide the fibers, yarns, carpets, and fabrics with dimensional stability. A steaming unit made by Superba of Mulhouse, France or American Superba, Inc. of Charlotte, N.C. is typical of the equipment employed in heatsetting with moist heat. Typically, the heatsetting temperature for nylon 6 is in the range of 124° C. to 127° C. Polyamide fibers, yarns, carpets, and fabrics often shrink during heatsetting. The typical heatset shrinkage encountered with 100 percent nylon 6 fibers, etc. is about 24 percent to about 32 percent. High heatset shrinkage can hurt carpet wear performance and appearance; therefore, less heatset shrinkage is desirable. One way of obtaining less shrinkage is to heatset nylon 6 fibers, yarns, carpets, and fabrics at a lower temperature. Heatsetting at a lower temperature is advantageous because it provides an environment that is not as harsh and results in a savings of both energy and energy costs. Commonly, however, lower heatset temperatures are undesirable because the resulting carpet product lacks the characteristics of acceptable appearance and wear performance required by the marketplace. For example, the resulting carpet product sometimes shows streaks and chevrons when dyed and may lack properties such as good tip definition and good cover.